Unusual Concentration of Tc-99m methylendiphosphonate in Rhabdomyosarcoma.

Extraosseous accumulation of bone-seeking agents is rare, but has been previously reported in pediatric sarcomas and neuroblastomas. We present an unusual case of a 5-month-old male with an abdominal mass observed clinically by his parents and referring pediatrician. Contrast abdominal computerized tomography confirmed the presence of a large pelvic mass that was diagnosed pathologically as embryonal rhabdomyosarcoma. A bone scintigraphy that was performed for staging of the disease revealed accumulation of the radiopharmaceutical in the tumor. There was no evidence for skeletal metastatic disease. This case further demonstrates the nonspecificity of soft-tissue tumor uptake on bone scintigraphy.